Chicago Zoological Society, Brookfield, Illinois, United States of America.
PLoS One. 2013 Aug 6;8(8):e72452. doi: 10.1371/journal.pone.0072452. Print 2013.
Many wildlife species are propagated in captivity as models for behavioral, physiological, and genetic research or to provide assurance populations to protect threatened species. However, very little is known about how animals evolve in the novel environment of captivity. The histories of most laboratory strains are poorly documented, and protected populations of wildlife species are usually too small and too short-term to allow robust statistical analysis. To document the evolutionary change in captive breeding programs, we monitored reproduction and behavior across 18 generations in six experimental populations of Peromyscusleucopus mice started from a common set of 20 wild-caught founders. The mice were propagated under three breeding protocols: a strategy to retain maximal genetic diversity, artificial selection against stereotypic behaviors that were hypothesized to reflect poor adaptation to captivity, and random bred controls. Two replicates were maintained with each protocol, and inter-replicate crosses at generations 19 and 20 were used to reverse accumulated inbreeding. We found that one of the stereotypic behaviors (repetitive flipping) was positively associated with reproductive fitness, while the other (gnawing) was relatively invariant. Selection to reduce these stereotypic behaviors caused marked reduction in reproduction, and populations not under artificial selection to reduce these behaviors responded with large increases in flipping. In non-selected populations, there was rapid evolution toward much higher proportion of pairs breeding and more rapid conception. Litter size, pup survival, and weaning mass all declined slowly, to the extent that would be predicted based on inbreeding depression. Inter-crossing between replicate populations reversed these declines in fitness components but did not reverse the changes in behavior or the accelerated breeding. These findings indicate that adaptation to captivity can be rapid, affecting reproductive patterns and behaviors, even under breeding protocols designed to minimize the rate of genetic change due to random drift and inadvertent selection.
许多野生动物物种被圈养作为行为、生理和遗传研究的模型，或者为保护濒危物种提供保障种群。然而，对于动物在圈养的新环境中是如何进化的，我们知之甚少。大多数实验室品系的历史记录都很差，野生动物保护种群通常太小且时间太短，无法进行稳健的统计分析。为了记录圈养繁殖计划中的进化变化，我们在 6 个 Peromyscus leucopus 实验种群中监测了 18 代的繁殖和行为，这些种群是由 20 只野生捕获的祖先共同建立的。这些老鼠在三种繁殖方案下繁殖：一种是保留最大遗传多样性的策略，一种是针对假设反映对圈养适应性差的刻板行为进行人工选择的策略，还有一种是随机繁殖对照的策略。每种方案都维持了两个重复，在第 19 和 20 代进行了重复间交叉，以逆转积累的近交。我们发现，一种刻板行为（重复翻转）与繁殖适应性呈正相关，而另一种行为（啃咬）则相对不变。为了减少这些刻板行为而进行的选择导致繁殖率显著下降，而没有受到减少这些行为的人工选择的种群则以大幅增加翻转反应。在未选择的种群中，繁殖的比例迅速向更高的比例发展，受孕速度也更快。窝仔数、幼仔存活率和断奶体重都缓慢下降，下降幅度与基于近交衰退的预测相符。在重复种群之间进行交叉可以逆转这些适应能力的下降，但不能逆转行为的变化或加速繁殖。这些发现表明，即使在旨在最小化由于随机漂移和不经意选择导致遗传变化的繁殖方案下，对圈养的适应也可以很快发生，影响繁殖模式和行为。
